Question

I’m trying to create a sort descriptor, for a core data fetch request, that will fetch objects that are ordered by a calculated value (e.g., the sum of two or more attributes). Is this possible? Thanks in advance.

Answer 1

From the “Core Data Programming Guide”:

You cannot fetch using a predicate based on transient properties
(although you can use transient properties to filter in memory
yourself). … To
summarize, though, if you execute a fetch directly, you should
typically not add Objective-C-based predicates or sort descriptors to
the fetch request. Instead you should apply these to the results of
the fetch.

So sorting by a calculated value seems not to be possible. You have to pre-calculate the sorting value and store it as (non-transient) attribute in your objects.